TW202123329A - Asymmetry correction via oriented wafer loading - Google Patents

Abstract

A chemical mechanical polishing system includes a metrology station having a sensor configured to measure a thickness profile of a substrate, a robotic arm configured to transfer the substrate from the metrology station to a polishing station having, a platen to support a polishing pad having a polishing surface, a carrier head on the polishing surface, the carrier head having a membrane configured to apply pressure to the substrate in the carrier head, and a controller configured to receive measurements from the sensor and configured to control the robotic arm to orient the substrate in the carrier head according to substrate profile and a removal profile for the carrier head.

Description

Asymmetry correction via oriented wafer loading

The present disclosure relates to chemical mechanical polishing (CMP).

Generally, an integrated circuit is formed on a substrate by sequentially depositing a conductive layer, a semiconductor layer, or an insulating layer on a semiconductor wafer. Various manufacturing processes require planarization of the layers on the substrate. For example, one manufacturing step involves depositing a filler layer on a non-planar surface and planarizing the filler layer until the non-planar surface is exposed. For some applications, the filler layer is planarized until the top surface of the patterned layer is exposed. For example, a metal layer can be deposited on the patterned insulating layer to fill trenches or holes in the insulating layer. After planarization, the remaining portions of the metal in the grooves and holes of the patterned layer are formed with vias, inserts and wires to provide conductive paths between the thin film circuits on the substrate. As another example, a dielectric layer can be deposited on the patterned conductive layer and then planarized to achieve subsequent photolithography steps.

Chemical mechanical polishing (CMP) is an accepted method of planarization. This planarization method usually requires mounting the substrate on the carrier head. The exposed surface of the substrate is usually placed against the rotating polishing pad. The carrier head provides a controllable load on the substrate to push the substrate toward the polishing pad. The polishing slurry with abrasive particles is usually supplied to the surface of the polishing pad.

In one aspect, a chemical mechanical polishing system includes: a metering station having a sensor configured to measure the thickness profile of a substrate; a robotic arm configured to transfer the substrate from the metering station to the polishing station, the polishing station having: A platform for supporting a polishing pad with a polishing surface; a carrier head on the polishing surface, the carrier head having a membrane configured to apply pressure to the substrate in the carrier head; and a controller configured to receive the sensor The measurement result is configured to control the robotic arm to orient the substrate in the carrier head according to the contour of the substrate and the removal profile of the carrier head.

Specific embodiments of any of the foregoing aspects may include one or more of the following features.

The fixing ring can enclose the substrate in the carrying head. The diameter of the substrate may be 1-3 mm smaller than the diameter of the inner surface of the retaining ring.

The sensor may be a camera.

The sensor can be configured to perform a line scan.

The carrier head may have one or more marks indicating the orientation of the carrier head.

The substrate may have one or more markings indicating the orientation of the substrate. The mark can be a notch or a flat surface on the substrate.

The controller can assign a mark indicating the orientation of the substrate.

The base of the metering station can support the substrate.

In another aspect, a method of chemical mechanical polishing includes: measuring the thickness of the first substrate; determining the thickness profile of the first substrate according to the measured thickness; transferring the first substrate to the carrier head, and loading the first substrate on the carrier In the head, the first substrate and the carrier head are at a zero position; the first substrate is polished; the polishing thickness of the first substrate is measured; the first substrate polishing thickness profile is determined according to the measured polishing thickness; by comparing the first substrate thickness profile Calculate the removal profile caused by the carrier head by grinding the thickness profile of the first substrate; measure the thickness profile of the second substrate; rotate the carrier head to a desired angle relative to the second substrate, where the carrier head is oriented at a desired angle relative to the second substrate , Configured to reduce the thickness profile of the second substrate by removing the contour; transferring the second substrate to the carrying head, and loading the second substrate into the carrying head; and grinding the second substrate.

Specific embodiments of any of the foregoing aspects may include one or more of the following features.

A fixing ring is used to hold the first substrate and the second substrate in the carrier head.

The sensor can be used to measure the thickness of the first substrate, the grinding thickness of the first substrate, and the thickness of the second substrate. The sensor may be a camera. The sensor can be used to perform line scanning.

The marks on the carrier head may be aligned with the marks on the first substrate. The mark on the first substrate may be a notch or a flat surface of the first substrate.

The marks on the carrier head may be aligned at a certain angle with respect to the marks on the second substrate. The mark on the second substrate may be a notch or a flat surface of the second substrate.

The advantages of the above content may include (but are not limited to) the following advantages. The asymmetry of the substrate can be reduced by orienting the substrate in the carrier head to at least partially offset the asymmetric thickness profile of the substrate using the removal profile of the carrier head. This can improve the uniformity within the wafer and the uniformity between the wafers.

The details of one or more specific embodiments are disclosed in the attached drawings and the following description. According to the description and drawings, as well as the scope of patent application, it will be obvious to understand other aspects, features and advantages.

In some polishing systems, the membrane in the carrier head is used to apply pressure on the substrate during polishing. However, even if the carrier head is operated in a manner intended to apply uniform pressure on the substrate, the substrate can be subjected to an asymmetric removal profile, that is, the amount of removal varies with the angular position around the center of the substrate (rather than only from the center to the radial direction). The distance varies). This asymmetry may be caused by processing changes on the entire substrate or the pressure difference with the carrier head, even if the chamber in the carrier head is uniformly pressurized. Furthermore, before grinding, the substrate may have an initial asymmetrical non-uniform thickness profile. The combination of the asymmetric removal profile and the initial asymmetric thickness profile of the substrate can result in a highly asymmetric final thickness profile of the polished substrate.

One solution to this problem is to determine a specific removal profile of the carrier head and orient the substrate in the carrier head so that the removal profile and the thickness profile of the substrate at least partially cancel each other out, thereby reducing the asymmetry of the final thickness profile.

FIG. 1 shows an example of a grinding system 100 including a grinding device 104. The grinding device 104 includes one or more carrier heads 140 (only one is shown). Each carrier head 140 is operable to hold the substrate 10 such as a wafer against the polishing pad 110. The carrier head 140 may have independent control of the polishing parameters (such as pressure) associated with each individual substrate. Each carrier head 140 includes a holding ring 142 to hold the substrate 10 on the polishing pad 110 and in a position under the flexible film 144.

The carrier head 140 may optionally include a plurality of independently controllable pressure chambers defined by the membrane, for example, three chambers 146a-146c. The chambers 146a-146c can apply independently controllable pressure to the flexible membrane 144 (and therefore On the substrate 10) associated partitions.

The carrying head 140 is suspended by a supporting structure 150 (for example, a rotating material rack or a rail), and is connected to the carrying head rotating motor 154 by a driving shaft 152 so that the carrying head can rotate along the shaft 155. Optionally, each carrying head 140 may vibrate laterally on a slider on the support structure 150, for example, by the rotation vibration of the rotating material rack itself, or by the movement of a bracket supporting the carrying head 140 along the track.

The polishing device 104 includes a platform 120, the platform 120 is a rotatable dish-shaped platform, and the polishing pad 110 is located on the platform 120. The platform can be operated to rotate along the axis 125. For example, the motor 121 can rotate the drive shaft 124 to rotate the platform 120. The polishing pad 110 may be a double-layer polishing pad having an outer polishing layer 112 and a softer backing layer 114.

The polishing device 104 may include a through port 130 to release a polishing liquid 132 (such as a slurry) onto the polishing pad 110 to the pad. The polishing equipment may also include a polishing pad adjuster to polish the polishing pad 110 to maintain the polishing pad 110 in a consistent abrasive state.

During operation, the platform 120 rotates along the central axis 125 of the platform, and each carrier head 140 rotates along the central axis 155 of the carrier head and is displaced laterally across the top surface of the polishing pad. Generally, the rotation of the carrier head 140 causes the substrate 10 to rotate at the same rotation rate. Without being bound by any particular theory, although the substrate is not "sticked" to the film 144 in the carrier head 140, the friction of the inner surface of the rotating fixed ring 142 with respect to the edge of the substrate 10 will result in an equal speed of the rotating substrate 10 .

Although only one carrier head 140 is shown, more carrier heads can be provided to hold additional substrates, so that the surface area of the polishing pad 110 can be used efficiently. Therefore, the number of carrier head assemblies suitable for holding a substrate for simultaneous polishing may be based at least in part on the surface area of the polishing pad 110.

In some embodiments, the grinding equipment includes an in-situ monitoring system 160. The in-situ monitoring system may be an optical monitoring system, such as a spectrum monitoring system, which may be used to measure the spectrum of reflected light from a substrate undergoing grinding. An optical channel through the polishing pad is provided by including a hole (ie, a hole through the polishing pad) or a solid window 118. The in-situ monitoring system may alternatively or additionally include an eddy current monitoring system.

In some embodiments, the optical monitoring system 160 is an in-sequence optical monitoring system that has a probe (not shown) positioned between two grinding devices or between the grinding device and the transfer station. The monitoring system 160 may continuously or periodically monitor one or more characteristics of the area of the substrate during grinding. For example, one feature is the thickness of each area of the substrate.

In an in-situ or sequential embodiment, the optical monitoring system 160 may include a light source 162, a light detector 164, and a circuit for sending and receiving signals between, for example, a remote controller 190 of a computer, the light source 162, and the light detector 164. System 166. One or more optical fibers 170 may be used to transmit the light from the light source 162 to the optical channel in the polishing pad, and transmit the light reflected from the substrate 10 to the detector 164.

Referring to FIGS. 1-3, the carrier head 140 is configured to tightly surround the substrate 10 at its edges. For example, the diameter of the substrate 10 is smaller than the diameter of the inner surface of the retaining ring 142 of the carrier head 140 by 1-3 mm. When the substrate 10 is ground in the carrier head 140, the edge of the substrate 10 (for example, the front edge of the substrate 10) rolls on the inner surface of the carrier head 140, for example, on the inner surface of the fixed ring 142. Due to the friction between the front edge of the substrate 10 and the inner surface of the carrier head 140, the substrate 10 can roll against the inner surface of the carrier head 140 (for example, against the inner surface of the retaining ring 142), so that when the carrier head 140 rotates The substrate 10 rotates accordingly. Hypothetically, the rotation of the substrate 10 will even cancel out the asymmetric grinding effect due to, for example, the difference in relative speed between the regions closer or farther from the rotation axis of the platform. However, in reality, since the substrate is maintained at a substantially fixed angular position relative to the carrier head, the substrate 10 may be affected by the unique removal profile of the carrier head 140. The removal profile of the carrier head can be determined as follows, for example, determined based on experience, and then stored for use in selecting the orientation of the substrate during loading.

2 and 3, before being loaded into the carrier head 140 and polished by the polishing device 104, the pre-polished thickness profile of the substrate 10 is determined. In order to determine the thickness profile before grinding, the substrate 10 can be loaded on the base 182 of the metering station 180. The sensor 186 is configured to measure the thickness of the substrate 10, for example, the thickness (including the thickness difference) of the outermost layer deposited on the substrate. The thickness of the substrate 10 can be measured at a plurality of positions in the two-dimensional array across the substrate 10. The sensor 186 may be, for example, a camera or other similar metrology device configured to scan the substrate 10. For example, the sensor 186 may perform a line scan of the substrate 10 to generate a two-dimensional color image of the substrate. The sensor 186 can generate a thickness measurement value, or a measurement value that scales linearly with the thickness.

In order to measure the thickness of the substrate 10, the sensor 186 may measure selected points in a circle around the center of the substrate 10 at the same radial distance from the center of the substrate 10, for example. For example, the base 182 may be rotated so that the sensor 186 scans a circular path on the substrate 10. In some embodiments, the sensor 186 can measure at multiple angular positions around the center of the substrate and at multiple radial distances from the center of the substrate 10; these can be at multiple different radii on the substrate 10. The angle profile is provided in the circle of. Alternatively, the sensor 186 may perform measurement on the entire substrate 10 in a regular array (for example, a rectangular array) to form a two-dimensional array of the thickness of the substrate 10.

The sensor 186 measurement value may be sent to the controller 190, and the controller 190 may then process the measurement value to generate the thickness profile of the substrate 10. For example, the measurement results can be combined to generate a thickness profile of the substrate 10, such as an angular thickness profile. The angular thickness profile may indicate the thickness of the substrate 10 at different angular positions around the center of the substrate 10. For example, for each of a plurality of angles around the center of the substrate 10, the angular thickness profile may indicate an average thickness value at a radial distance from the center of the substrate 10. The angular thickness profile may also indicate the thickness of the substrate at different angular positions at a plurality of different radial distances from the center of the substrate 10. Alternatively, the thickness profile may be a two-dimensional array of the thickness of the substrate 10 measured by the sensor 186 and generated by the controller 190.

After determining the thickness profile of the substrate 10, the desired orientation of the substrate 10 in the carrier head 140 is calculated. As described above, the controller 190 may store the removal profile of the carrier head 140. For example, the controller 190 may store a plurality of thickness removal values, the thickness removal value being a function of the angle with respect to the center of the substrate.

儘管可以使用其他差異度量，例如差異的絕對值之和。The substrate 10 may be positioned in the carrier head 140 such that the asymmetry in the final thickness profile is at least partially offset by the asymmetry in the removal profile of the carrier head. _{The controller may be configured to determine the desired relative orientation θ D of the} substrate 10 with respect to the carrier head 140 based on the known removal profile R _H (θ) of the carrier head 140 and the pre-polished thickness profile R _{S (θ) of the substrate 10} . For example, the angle difference Δθ may increase in a range of, for example, every 1 degree or every 5 degrees between 0 degrees and 360 degrees. At each value of Δθ, calculate the total difference between the _{known removal profile R H} (θ) and the pre-grind thickness profile R _{S (θ).} The total difference can be calculated as the sum of the squares of the difference, for example,

Although other difference measures can be used, such as the sum of absolute differences.

The desired angle θ _D should be equal to the value of Δθ that provides the minimum value for the total difference.

The carrier head may rotate relative to the substrate to have a desired angle θD. In other words, the carrier head 140 can be rotated to a certain angle, so that the removal profile of the carrier head 140 is complementary to the pre-grinding thickness profile of the substrate 10. For example, the carrier head 140 may be rotated relative to the substrate 10 so that during grinding, the maximum removal part of the removal profile may correspond to the thickest part of the pre-grind thickness profile.

In order to place the substrate 10 in the carrier head 140 in a desired orientation, as described above, the desired relative angle θ _D between the carrier head 140 and the substrate 10 is calculated.

The absolute angular position θ _{P of the} substrate 10 (for example, relative to the fixed frame of the polishing device) is measured. When the substrate 10 is on the base 182, it can be measured by the sensor 186. For example, an optical sensor may be used for measurement, and the optical sensor may detect marks on the substrate 10, such as notches or flat surfaces (for example, B in FIG. 3). Based on the absolute angular position of the substrate on the base, the controller can calculate the absolute angular position θ _{S of the} substrate when the substrate is loaded into the carrier head 140. _{The difference between θ P} and θ _S can be determined according to the predetermined movement when the robot 184 moves the substrate from the base 182 to the carrier head 140, for example, if the robot 184 rotates the substrate 10 by 90° or 180° when moving the substrate.

_{The absolute angular orientation θ H of the} carrier head can be measured, for example, by optically detecting a mark (such as position A or C) on the carrier head 140 or using a motor encoder 188 that measures the rotation of the carrier head 140.

Once the absolute angular position θ _{S of the substrate 10 and the required relative angle θ D} between the substrate 10 and the carrier head 140 are determined, the carrier head 140 is rotated to an absolute angular orientation to provide the required angle θ D relative to the substrate 10 , For example, θ _H =θ _S +θ _D. The controller 190 can be used to rotate the carrier head 140 to a proper angular orientation using feedback from an encoder or an optical monitor.

Then, the controller 190 may cause the robot arm 184 to transfer the substrate 10 from the metering station 180 (for example, from the base 182) to the carrier head 140.

When the substrate 10 is loaded in the carrier head 140, the polishing of the substrate 10 in the carrier head 140 results in a polishing profile with lower asymmetry, because the removal profile of the carrier head reduces the thickness profile of the substrate 10 Asymmetry.

The test substrate 10 can be used to determine the removal profile of the carrier head 140. First, before loading the substrate 10 into the carrier head 140, the sensor 186 can measure the pre-polished thickness profile of the substrate 10. For example, the pre-polished thickness profile of the substrate 10 can be measured at the metering station 180. Then, using the robotic arm 184, the substrate 10 can be transferred from the metering station 180 and loaded into the carrier head 140, where both are in a "zero position" (or other known position and orientation) relative to each other. For example, the position mark B of the substrate 10 and the position mark A of the carrier head 140 may be aligned. The substrate 10 can then be polished in the carrier head 140. After polishing, the robotic arm 184 can be used to transfer the substrate 10 from the carrier head 140 to the metering station 180, where the thickness profile of the substrate 10 after polishing can be measured. Then, the removal contour of the carrier head 140 can be calculated by comparing the thickness contours of the substrate 10 before and after the polishing, for example, subtracting the contour before the polishing from the contour after the polishing.

When the carrying head 140 is worn, the carrying head 140 can be replaced. The replacement carrier head 140 will also have a unique removal profile. In order to measure and calibrate the removal profile of each carrier head 140, the substrate (for example, a test substrate for each replacement carrier head 140) may be ground to determine the removal profile of the carrier head 140. The comparison of the thickness profile and the grinding profile can determine the removal profile of the carrier head 140. For example, the controller 190 compares the measurement result of the thickness profile of the substrate 10 before polishing in the carrier head 140 with the polished thickness profile of the substrate 10 after polishing in the carrier head 140. Comparing the thickness profile and the grinding profile of the substrate 10 reveals the removal profile due to the carrier head 140 (for example, the radial profile due to the pressure in the carrier head 140).

The controller and other computing device parts of the system described herein can be implemented by a digital electronic circuit system, or implemented by computer software, firmware, or hardware. For example, the controller may include a processor to execute a computer program such as stored in a computer program product (eg, in a non-transitory machine-readable storage medium). Computer programs (also called programs, software, software applications, or codes) can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, or subroutine , Or other units suitable for use in a computing environment.

Although this document contains many specific implementation details, these details should not be construed as limitations on the scope of any specific embodiment of the present disclosure or the content that can be requested, but as features specific to specific embodiments of the specific invention. description of. Certain features described in the background content of individual specific embodiments in this document can also be combined and implemented in a single specific embodiment. In contrast, various features described in the background content of a single specific embodiment can also be implemented in multiple specific embodiments individually or in any suitable sub-combination. Furthermore, although features may be described above as functioning in certain combinations and even initially claimed as such, one or more features from the claimed combination may in some cases be deleted from the combination, and the claimed The combination of can be for sub-combination or sub-combination changes.

Several specific embodiments of the present invention have been described. However, it should be understood that various modifications can be made without departing from the spirit and scope of the present invention. Therefore, there are other embodiments within the scope of the following patent applications.

10: substrate 100: Grinding system 104: Grinding equipment 110: Grinding pad 112: Outer polishing layer 114: back support layer 118: solid window 121: Motor 124: drive shaft 125: axis 130: Port 132: Grinding liquid 140: Carrying head 142: fixed ring 144: Membrane 146a: Chamber 146b: Chamber 146c: Chamber 150: support structure 152: drive shaft 154: Motor 155: Shaft 160: In-situ monitoring system 162: light source 164: Light detector 166: Circuit System 170: Fiber 180: Metering station 182: Base 184: Robot 186: Sensor 188: Motor encoder 190: Controller

Fig. 1 is a schematic cross-sectional view of the polishing system.

Figure 2 is a schematic diagram of a substrate loading station, a metering station, and a polishing system.

Figure 3 is a schematic top view of a substrate oriented in a carrier head of a polishing system.

Domestic deposit information (please note in the order of deposit institution, date and number) no Foreign hosting information (please note in the order of hosting country, institution, date, and number) no

10: substrate

104: Grinding equipment

110: Grinding pad

140: Carrying head

142: fixed ring

180: Metering station

182: Base

184: Robot

186: Sensor

188: Motor encoder

190: Controller

Claims (20)

A chemical mechanical polishing system, including: A polishing station, the polishing station having a platform for supporting a polishing pad, a carrying head for holding a substrate, and a motor for rotating the carrying head; A robotic arm configured to transfer the substrate to the polishing station; and A controller configured to store an angular removal profile of the carrier head and receive an angular thickness profile of the substrate to determine the carrier head relative to the substrate based on the angle removal profile and the angular thickness profile A loading orientation, so that the motor rotates the carrying head so that the carrying head is in the loading orientation, and the substrate is loaded into the carrying head when the carrying head is in the loading orientation. The system according to claim 1, wherein the controller is configured to determine a loading orientation to reduce the angular asymmetry in the final thickness profile determined based on the angle removal profile and the angular thickness profile. The system according to claim 1, wherein the controller is configured to use the angle difference as the angle offset between the angle removal profile and the angle thickness profile to calculate the angle difference for each of the plurality of angle differences. A total thickness difference between the angle removal profile and the angle thickness profile and a final thickness profile. The system according to claim 3, wherein the controller is configured to select an angle difference with the smallest total thickness difference from the plurality of angle differences. The system of claim 3, wherein the controller is configured to determine the angular orientation based on the angular difference. The system according to claim 3, wherein the controller is configured to calculate the final thickness profile as the sum of the least square difference between the angle removal profile and the angle thickness profile. The system according to claim 1, the system comprising a metering station having a sensor configured to measure the angular thickness profile of the substrate. The system according to claim 7, wherein the sensor includes a line scan camera. According to the system of claim 1, the system includes a sensor that determines an angular orientation of the substrate before loading the substrate into the carrier head. The system according to claim 9, wherein the sensor is configured to detect a mark on the substrate. The system according to claim 10, wherein the sensor is configured to detect a flat surface or a notch on the substrate. The system of claim 10, wherein the controller is configured to assign a mark indicating the orientation of the substrate. The system according to claim 9, the system includes a metering station to measure the angular thickness profile of the substrate, and wherein the sensor is located in the metering station to determine an angular orientation of the substrate in the metering station. The system according to claim 1, wherein the substrate has one or more marks indicating the orientation of the substrate. A method of chemical mechanical polishing, the method includes the following steps: Receiving a measurement of the thickness profile of a corner of a substrate; Choose a desired angle for the carrier head relative to the substrate to reduce the unevenness of the grinding angle; Rotate the carrying head to the required angle; Transfer the substrate to the carrier head, and load the substrate into the carrier head together with the carrier head at a desired angle; and Grind the substrate. The method described in claim 15, which includes the following steps: Measuring an angular thickness profile of a test substrate before polishing; Loading the test substrate into the carrying head, and the carrying head is at a zero position relative to the substrate; Grinding the test substrate; Measuring an angular thickness profile of the test substrate after grinding; By comparing the angular thickness profile before grinding and the angular thickness profile after grinding, an angular removal profile due to the carrier head is calculated. According to the method of claim 15, the method further includes the following steps: aligning the carrier head with a mark on the substrate. The method according to claim 17, wherein the mark is a notch or flat surface of the substrate. A method of chemical mechanical polishing, the method includes the following steps: Measuring the thickness of a first substrate; Determining a first substrate thickness profile according to the measured thickness; Transferring the first substrate to a carrying head, and loading the first substrate into the carrying head, wherein the first substrate and the carrying head are at a zero position; Grinding the first substrate; Measuring the grinding thickness of the first substrate; Determining the grinding thickness profile of the first substrate according to the measured grinding thickness; Calculating a removal profile caused by the carrier head by comparing the thickness profile of the first substrate with the grinding thickness profile of the first substrate; Measuring the thickness profile of a second substrate; Rotating the carrier head to a desired angle with respect to the second substrate, wherein the orientation of the carrier head at a desired angle with respect to the second substrate is configured such that the removal profile reduces the thickness profile of the second substrate; Transferring the second substrate to the carrying head, and loading the second substrate into the carrying head; and Grind the second substrate. A chemical mechanical polishing system, including: A metering station having a sensor configured to measure a thickness profile of a substrate; A polishing station having a platform to support a polishing pad with a polishing surface, the polishing station having a bearing head that holds the substrate against the polishing surface, and the bearing head having a bearing head configured to support the bearing A membrane in the head that applies pressure to the substrate; A robotic arm configured to transfer the substrate from the metering station to the polishing station; A controller configured to receive the measurement result from the sensor and configured to control the robotic arm to orient the carrier head in accordance with the substrate profile and a removal profile for the carrier head Substrate.

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